And that’s just the stuff that’s larger than a centimeter. Even tinier bits of artificial material could number in the tens of millions, according to NASA’s Orbital Debris Program Office.

The problem is that once we’ve launched something into a stable orbit, we usually don’t have a way to get it back down. Many satellites, for instance, were launched without a firm lifespan in mind, so they just keep going until communications cease due to loss of power or malfunctions.

Without communications, mission managers on the ground have no way to tell the probe to deorbit—and even if they could, there’s no guarantee the craft could be brought down safely.

Considering that, of the thousands of objects launched since the dawn of the space age, only a thousand or so currently work, there’s an awful lot of dead satellites just hanging around up there.

And like plastics that take ages to break down in landfills, orbiting objects can take hundreds of years to fall from the sky. The oldest piece of space debris up there right now is Vanguard 1, a defunct U.S. satellite launched in 1958 that’s expected to stay in orbit for a total of 240 years.

Other big pieces of space junk come from the spent upper stages of rocket boosters and even from equipment lost during spacewalks, such as the toolkit lost by an astronaut during a November 2008 space shuttle mission.

Space junk is flying around up there at anywhere from 4.3 to 6.2 miles (7 to 10 kilometers) a second—so fast that even a fleck of paint can cause pitting in the window of a space shuttle:

A nearly three-millimeter-wide crater in the window of the shuttle Challenger after a 1983 flight.

—Image courtesy NASA

Collisions with even a small speck can damage working satellites or harm spacewalkers. And larger pieces left up there will eventually come down, creating potential hazards if they do not completely disintegrate during reentry.

Not to mention that space junk is only increasing with each new launch—some experts say at a rate of 5 percent a year. That much clutter invariably blocks communications signals, making it harder to get reliable data streams from satellites surrounded by junk.

For now, the old adage of “reduce, reuse, recycle” is complicated in space, which is difficult/expensive to get to and thus hard to clean up.

But it’s gotta start somewhere, which is why folks at the U.K.’s Surrey Space Centre are proposing a plan: Send any future craft into orbit with their new “nanosatellite,” which contains a deployable solar sail.

The 16.4×16.4-foot (5×5-meter) CubeSail blossoms from a 3.9×3.9×11.8-inch (10x10x30-centimeter) instrument, which can be instructed to deorbit a nonoperational craft of up to 1,102 pounds (500 kilograms).

The device is compact and lightweight, because rather than running on regular fuel, the sail is pushed by solar radiation, while tiny rudder-like motors in the main body are used to direct the ensemble into a downward spiral.

Announced on March 25, prototype CubeSails are slated for launch by late 2011.

“Successful deployment and testing of the sail can enable a low cost/mass solution to be used for future satellites and launch vehicle upper stages reducing dramatically the problem of space debris,” SSC project leader Vaios Lappas said in a statement.

The scientists also hope to launch CubeSails by 2013 that can be directed to glom on to existing space debris, effectively creating a fleet of remote-controlled litter collectors.

This may prove more of a challenge, since getting unattached CubeSails into space would involve roughly the same level of effort as launching a full-size spacecraft. Such concerns are exactly why previously proposed solutions for retrieving or otherwise redirecting space junk have stayed on project shelves.

But as with any environmental dilemma, it’s good to know there are people out there giving serious thought to a viable solution.

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